1. Field of the Invention
The present invention relates to a cooling device for electronic parts, which cools heat-generating electronic parts such as a microprocessor (hereinafter referred to as a CPU) installed in a housing by the circulation of refrigerant.
2. Description of the Related Art
In recent years, computer speed increases rapidly, and thus the clock frequency of the CPU becomes extremely large as compared to that of the old days. As a result, the amount of heat generated by the CPU increases considerably, and thus the computer cannot be cooled sufficiently only by the air cooling of a heat sink, and it is indispensable to install a high-efficiency and high-output cooling device. As a result, a cooling device that circulates refrigerant to cool a board on which heat-generating electronic parts are mounted is proposed as the cooling device (see JP-A-7-142886).
Hereinafter, a related cooling device for electronic parts, which circulates refrigerant to cool the electronic parts, will be described. The cooling device shown in FIG. 8 is a related cooling device for electronic parts in the related art (see JP-A-7-142886). The cooling device transfers the heat generated by the heat-generating parts to a metallic housing that is a heat-radiating portion, efficiently so as to cool the heat-generating members. FIG. 8 illustrates the structure of the related cooling device for an electronic apparatus.
In FIG. 8, a reference numeral 108 is a circuit board of an electronic apparatus, a reference numeral 109 is a keyboard, a reference numeral 110 is a semiconductor heating element, a reference numeral 111 is a disc device, a reference numeral 112 is a display device, a reference numeral 113 is a heat-receiving header that exchanges heat with the semiconductor heating element 110, a reference numeral 114 is a heat-radiating header for radiating heat, a reference numeral 115 is a flexible tube, and a reference numeral 116 is the metallic housing of the electronic apparatus.
The cooling device thermally connects the semiconductor heating element 110, which is a heat-generating member, with the metallic housing 116 via a heat transfer device having a flexible structure. The heat transfer device is constituted with the flat heat-receiving header 113 having a liquid passage attached to the semiconductor heating elements 110, the heat-radiating header 114 that is in contact with a wall of the metallic housing 116 having a liquid passage, and the flexible tube 115 that connects the heat-receiving header 113 with the heat-radiating header 114. Also, the heat transfer device drives or circulates liquid that is enclosed in the heat transfer device between the heat-receiving header 113 and the heat-radiating header 114 by using a liquid driving mechanism built in the heat-radiating header 114. As a result, the semiconductor heating elements 110 and the heat-radiating header 114 can be easily connected with each other regardless of the arrangement of the parts, and heat is efficiently transferred by the driving of the liquid. Since the heat-radiating header 114 is thermally connected with the metallic housing 116, and the metallic housing 116 has high thermal conductivity, heat is dissipated widely throughout the metallic housing 116.
In addition, the present applicant proposed a turbo-type pump, as a heat-receiving pump, which can circulate a large amount of refrigerant and comes into contact with the heat-generating members to exchange heat. Also, the applicant proposed a technique in which a pump casing comes into close contact with heat-generating electronic parts to exchange heat (Japanese Patent Application No. 2003-374136).
Further, a design to form a recessed conical surface by a casing of a water pump is registered. However, since the registered design evidently has no relation to a pump for a cooling device, the above registered design cannot be applied to a pump for a cooling device (see Japanese Registered Design Publication No. 775382).
In the cooling device according to JP-A-7-142886, when the thermal conductivity of the heat-receiving header 113 is low, refrigerant cannot exchange heat with the heat-generating members. Also, since the heat exchange basically depends on the material of the refrigerant, heat can be exchanged within a certain extent, and thus the cooling efficiency cannot be further improved. In addition, since the structure of the liquid driving mechanism becomes complex, and the flow rate of the refrigerant becomes small in a reciprocating pump and the like, there is a limitation in making the cooling device smaller and in making the cooling device slimmer.
In addition, in the cooling device proposed by the applicant, it is possible to make the cooling device smaller, and to make the cooling device slimmer, and to cool the heat-generating members at a high-efficiency. However, it is necessary to increase the thermal conduction in the pump casing structurally, and to increase the heat transfer from the pump casing to the refrigerant in order to further improve the cooling efficiency. Particularly, since it is necessary to support an impeller of the pump in the vicinity of the suction port of the turbo-type pump, it is structurally impossible to transfer heat in the vicinity of the suction port, and thus to transfer heat. Also, the shape of the related pump casing has too large thermal resistance for dissipating heat throughout the casing, and also the shape of the pump casing has too large thermal resistance for transferring heat to the flow of the refrigerant.